What is Unix & Types of UNIX? || LN-TECHINFO

What is Unix?

UNIX is an operating system that was first developed in the 1960's, and has been under continuous development ever since. By operating system, we mean programs that do computer work. It is a stable, multi-user, multi-tasking system for servers, desktops and laptops.

UNIX systems also have a graphical user interface (GUI) similar to Microsoft Windows that is easy to use in the environment, however, the operation requires knowledge of UNIX, which is not covered by any graphical program, or when There is no Windows interface available, for example, in a telnet session.

Types of UNIX?

There are many different versions of Unix, although they share similar similarities. The most popular varieties of UNIX are Sun Solaris, GNU / Linux and MacOS X.

The UNIX operating system is made up of three parts; Kernel, Shell and Program

The kernel

The kernel of UNIX is the hub of the operating system: it allocates time and memory to the program and handles filestores and communications in response to system calls. As an example of the way shell and kernel work together, suppose a user type rm myfile (which has the effect of deleting the file myfile), the shell program searches the filestore for files containing rm, And then the program on myfile requests the kernel via a system call to execute rm. When the process rm myfile is finished, the shell returns the UNIX prompt% to the user, indicating that it is waiting for further commands.

The shell

The shell acts as an interface between the user and the kernel. When a user logs in, the login program checks the username and password, and then starts another program called Shell. Shell is a command line interpreter (CLI). It interprets commands in user types and arranges to exclude them. The commands themselves are programs: when they finish, the shell gives the user another hint (% on our system).

The skilled user can customize their own shell, and the user can use different shells on the same machine. The staff and students in the school have tcsh shell by default. Tcsh shell has some features to help user inputting commands. By typing a part of the file name completion, a command, the file name, or the directory name, and pressing the [Tab] key, the tcsh shell will automatically complete the remaining name. If the shell starts more than one name with the letters you typed, it will beep, prompting you to type a few more letters before pressing the tab key.

History - The shell maintains a list of the commands you typed. If you need to repeat a command, use the cursor keys to type or down the list for a list of previous commands.

Why use Unix?

Unix was developed on the basis of Philosophy that the power of a system comes from the relationship between programs, not programs themselves, UNIX programs are written to do a job well, and programs are written so that They work together, thus, Unix developers increase simplicity, portability and clarity in design. To follow this Philosophy, Unix systems are characterized by -

1. Use of text files for data storage.
2. A hierarchical file system.
3. A large number of small programs move together through a command-line interpreter.
4. Use of shell script.
5. Captive user interface is avoided.
6. Use of high-level language in operating systems.
7. Hierarchical File System.
8. Its syntax got wide use for regular expressions.
9. Unix shell inspired many command line interpreters who came after it.
10.  C programming language became more ubiquitous.
11. Helped to contribute to the explosion of the Internet by making TCP / IP protocols more widely available.
12. Contributed to the launch of the free software movement.

You can see the use of Linux everywhere. It is dominating our servers, desktops, smartphones and even used in some electrical appliances such as refrigerators.

Some people consider Unix and Linux to be Synonyms, but this is not true. Many operating systems were developed like Unix, but none of them gained popularity as Linux. Linux is a clone of Unix. It has many features similar to Unix, yet there are some major differences. Before Linux and Windows, Unix dominated the computer world. Unix is ​​a copyright name and IBM AIX, HP-UX and Sun Solaris are the only Unix operating systems.